1. Field of the Invention
The present invention relates to a variable capacity type swash plate compressor which is used for an automotive air conditioning system, or the like.
2. Description of the Related Art
There has been a conventional variable capacity type swash plate compressor (hereinafter simply referred to as a "compressor"). Such a conventional compressor is disclosed in Japanese Unexamined Utility Model Publication (KOKAI) No. 62-183,082 or Japanese Unexamined Utility Model Publication (KOKAI) No. 61-134,580. As illustrated in FIG. 12, the conventional compressor 600 includes a driving shaft 610 disposed in a crank chamber 601, a lug plate 620 engaged with and fixed to the driving shaft 610, a rotary driving member 630 connected to the lug plate 620 by way of a connecting pin 640, and a wobble plate 650 supported slidably with the rotary driving member 630. Further, the connecting pin 640 is adapted to swing the rotary driving member 630 back and forth (i.e., in the counterclockwise and clockwise directions in the drawing). Furthermore, a plurality of piston rods 660 are interposed between the wobble plate 650 and a plurality of pistons 670. Moreover, the pistons 670 are disposed reciprocally in a plurality of cylinder bores 680 which are formed in a cylinder block 690. Thus, the rotary movement of the driving shaft 610 is converted into the reciprocal movements of the pistons 670 by way of the rotary movement of the rotary driving member 630. In addition, the pressures in the crank chamber 601 control the inclination angles of the wobble plate 650, thereby varying the strokes of the pistons 670. As a result, the conventional compressor 600 can vary the discharge capacity.
In a supporter arm 621 of the lug plate 620, an arc-shaped slot 622 is formed so as to slidably guide the connecting pin 640 therein. The slot 622 enables the rotary driving member 630 and the wobble plate 650 to incline, and it also regulates the inclining operations. As a result, the top clearances of the pistons 670 can be always maintained virtually uniformly when the compression processes are completed.
When the wobble plate 650 is inclined to the maximum inclination angle and the discharge capacity of the conventional compressor 600 is varied to the maximum, the compression reactive forces act onto the wobble plate 650 by way of the pistons 670 and the piston rods 660, and they are supported with the slot 622 of the lug plate 620. In the conventional compressor 600, the acting points of the compression reactive forces on the wobble plate 650 and the supporting points thereof on the slot 622 are designed so that they are put on the lines which are parallel with the driving shaft 610. Hence, as the wobble plate 650 reduces the inclination angle, the supporting points of the compression reactive forces, acting onto the slot 622 by way of the connecting pin 640, descend in the slot 622, and the acting points of the compression reactive forces, acting onto the wobble plate 650 by way of the piston 670 at the top dead center position and the piston rod 660, ascend relatively with respect to the supporting points.
As a result, the acting points of the compression reactive forces, acting onto the wobble plate 650 by way of the piston 670 at the top dead center position and the piston rod 660, get further away from the driving shaft 610 than are the supporting points of the compression reactive forces, acting onto the slot 622 by way of the connecting pin 640. Consequently, there arise the moments in the clockwise direction in FIG. 12. The moments try to further reduce the inclination angle of the wobble plate 650 according to the compression reactive forces, and thereby they affect the discharge capacity reducing operation so as to be oversensitive. In addition, the moments also try to interfere with the discharge capacity increasing operation considerably, and thereby they affect the discharge capacity increasing operation so as to be dull. All in all, the conventional compressor is not satisfactory in the discharge capacity controllability.
Therefore, the present applicant thought of solving the problem, and he proposed and filed a Patent Application for a compressor with the Japanese Patent Office on Sep. 20, 1991 under Japanese Patent Application Serial No. 3-241,998 (U.S. Pat. No. 5,293,810). The Japanese application was not yet laid-open at the time of the present application, and accordingly it cannot be classified as prior art. The compressor comprises a hinge means which enables to maintain the top clearances of the pistons virtually uniformly in order to improve the discharge capacity controllability, and which inhibits the supporting points of the compression reactive forces from displacing.
As illustrated in FIGS. 10 and 11, the hinge means of the compressor proposed in the application includes a pair of supporter arms 41A, 41B, and a pair of guide pins 44A, 44B. The supporter arms 41A, 41B are disposed in a crank chamber 42 formed with a cylinder block 45, and the like, and they are projected rearwards (i.e., toward a swinging swash plate 46 (shown in FIG. 11) or away from viewers in the drawing) from a rotor 47 (shown in FIG. 11). The guide pins 44A, 44B are disposed in the crank chamber 42, and they are held rotatably with the supporter arms 41A, 41B at their heads, respectively, and they are inserted slidably into a pair of guide holes 43A, 43B at their legs, respectively. The guide holes 43A, 43B are formed in the swinging swash plate 46.
In the hinge means of the compressor proposed in the application, the supporting points "P.sub.1 " and "P.sub.2 " of the compression reactive forces are positioned at the heads of the guide pins 44A, 44B which are held rotatably with the supporter arms 41A, 41B, and they are inhibited from displacing when the swinging swash plate varies the inclination angles.
As a result, as illustrated in FIG. 11, the supporting points "P.sub.1 " and "P.sub.2 " of the compression reactive forces on the rotor 47, and the acting point "P.sub.a " thereof on the swinging swash plate 46 can be positioned at the same distance away from the driving shaft 47, and accordingly hardly any force moments are developed as a result of the compression reactive forces acting onto the swinging swash plate 46 by way of the pistons 48. Hence, the swinging swash plate 46 increases or decreases the inclination angle smoothly, thereby improving the discharge capacity controllability.
However, in the hinge means of the proposed compressor, spherical portions 44a, 44b are provided at the heads of the guide pins 44A, 44B which are held rotatably by the supporter arms 41A, 41B, and troublesome spherical machining must be carried out. Further, the following constructions are actually required in order to hold the spherical portions 44a, 44b with the supporter arms 41A, 41B. Namely, spherical holes must be formed in the supporter arms 41A, 41B, and they should be provided with outer ring bushings. The outer ring bushings are made dividable into two component parts having spherical concavities. Furthermore, the outer ring bushings should be inhibited from coming off with circular clips. Thus, in the hinge means, the number of the component parts tends to increase. Hence, the compressor might be associated with the raised manufacturing costs.